Apparatus for injecting a viscoelastic material in a subsurface pump



Sheet of 2 3 1968 R. P. VINCENT APPARATUS FOR INJECTING A VISCOELASTIC MATERIAL IN A SUBSURFACE PUMP Filed March 1, 1967 m R. E 9 B E l 3 8 O 6 8 v V 2 3 3 2 m I N v. t l A 2 E F F Y M B m 8 K 2 4 2 M 4 C o 2 O m 6 7 m 4 4 2 2 2 2 2 2 6 2 .l m m 4 l I I ATTORNEY TAKWF j A 5 2 M m l 2 2 2 United States Patent 3,418,938 APPARATUS FOR INJECTING A VISCOELASTIC MATERIAL IN A SUBSURFACE PUMP Renic P. Vincent, Tulsa, Okla., assignor to Pan American Petroleum Corporation, Tulsa, Okla., a corporation of Delaware Filed Mar. 1, 1967, Ser. No. 619,782 9 Claims. (Cl. 103-46) ABSTRACT OF THE DISCLOSURE An apparatus for injecting a viscoelastic material into the lower end of a string of tubing in a well bore through which a viscous oil is to be pumped. One of two strings of tubing contains a sucker rod string and the other contains the viscuous oil being produced. A viscoelastic material is injected down through the tubing string containing the .sucker rod through a hollow portion of the lower sucker rod through channels in the plunger to the space between the plunger and the pump barrel. An upper part of the plunger is smaller than the bottom part to permit the injection of the proper thickness of the film of the viscoelastic material.

This invention is related to the pumping of oil from deep wells. It is especially related to pumping of deep wells by rod-operated pumps and in which the fluid being pumped is a viscous oil.

Background When an oil well does not have suflicient energy to force the oil to the surface, some sort of artificial lift must be instituted. A very common method is to suspend a pump having a plunger and a barrel at the lower end of a string of tubing and actuate the pump by reciprocating a string of sucker rods. The lower end of the sucker rods is attached to the plunger and the upper end extends upwardly through the tubing to a power source at the surface. The pumping of the oil from the Well becomes rather diflicult as the oil becomes more and more viscous. Various methods have been tried in an effort to reduce the problem of pumping viscous oil. For example, additives have been added in an attempt to reduce the average viscosity of the oil during production. Heat has also been supplied to the production zone to lower the viscosity. More recently, as set out in US. Patent 3,196,947, a fluid which preferentially wets the wall of the production tubing is used. The wetting fluid hopefully effects lubrication between the viscous oil and the inner wall of the tubing and thus facilitates the upward flow of the viscous oil. The proper placing of the wetting agent is a crucial step. Novel means for placing a film of a selected material upon the wall of tubing are still needed.

Brief description of invention preferably of a liquid having a low viscosity and a decreased tendency to form a rough interface with and disperse into the viscous oil being pumped. This liquid is preferably a viscoelastic liquid. Many water soluble polymers form aqueous solutions which are viscoelastic, such as acrylamide-acrylate copolymers. Guar gum may also be used. A discussion of viscoelastic materials is given in the copending application 491,900, filed Sept. 30, 1965, and assigned to a common assignee with this present application.

Preferably, the plunger of the subsurface pump is modified to facilitate the forming of a film of a viscoelastic material of a desired thickness on the wall of the barrel. The lower part of the plunger has a diameter which has a conventional clearance with the inside diameter of the pump barrel. The upper portion of the plunger has a reduced diameter from that of the lower portion to have an upper clearance such that the desired thickness of the film of the viscoelastic material can be obtained when such material is forced in the upper clearance zone.

In an especially preferred embodiment, there are two parallel strings of tubing: the producing string through which the formation oil is pumped and the supply string which contains the string of sucker rods and also through which the viscoelastic fluid is supplied to the pump zone. The lower joint of the string of sucker rods is hollow to form a fluid supply passage therethrough. The upper end of this passage is connected to a conduit, e.g., the supply string of tubing, leading to the surface to a supply of viscoelastic liquid. The lower end of the supply passage within the lower joint of the sucker rod is in fluid communication with the annular clearance space between the upper smaller portion of the plunger and the barrel, called for convenience the upper clearance or film-shaping zone.

In this preferred embodiment, the string of tubing in which the sucker rods are suspended contains a viscoelastic material. This permits the sucker rods to fall more easily on the downstroke than in the conventional system wherein the sucker rods are in contact with the heavy viscous oil.

In operation, viscoelastic material is injected downwardly through the hollow sucker rod to the annular upper clearance Zone during operation of the pump, i.e., while viscous oil is being pumped. This produces a film on the wall of the pump. The viscoelastic material is a material which selectively contacts the steel. Continued injection of the viscoelastic material aids in maintaining a film on the interior wall of the tubing as pumping continues. Thus, the viscous oil will not tend to stick or cling to the tubing. The high viscosity oil goes upwardly with lubrication of the tubing provided by the viscoelastic material so that the resistance to flow of the viscous oil is decreased. The viscoelastic material also serves to lubricate the plunger so that it will fall easily on the downstroke, thus eliminating or reducing another difficulty in pumping viscous oil.

Various objects and a better understanding of the invention can be had from the following description taken in conjunction with the drawings in which:

FIGURE 1 illustrates a preferred embodiment of the invention;

FIGURE 2 illustrates a cross-section of the pump of FIGURE 2; and

FIGURE 3 illustrates another embodiment of the invention in which the viscous oil is pumped up the same tubing in which a hollow sucker rod string is suspended.

Attention is directed to FIGURE 1 which shows a preferred embodiment. Shown thereon are two parallel strings of tubing 10 and 12 suspended within a casing 13 in a borehole 14. String of tubing 12 can be referred to as the producing string, and as the viscoelastic liquid is pumped down string 10, it can be referred to as a supply string. A string of sucker rods 16 is suspended within tubing string 10 and extends upwardly through packing 18 at the top thereof to a conventional reciprocating power source not shown. The upper end of producing string d 12 is connected to suitable well head connections not shown.

A crossover-type tool or block 21 is suspended at the lower end of tubing 10. Block 21 has two vertical bores 21A and 21B which are adapted to be connected at their upper ends to string of tubing 12 and 10, respectively. Bore 21B extends vertically through crossover block 21. A slanting bore 21D has been provided to establish communication between vertical bore 21A and the lower portion of bore 21B. A plug 21C closes the bore 21D down stream of its intersection with vertical bore 21B. Tubing 10 is connected to block 12 as being threadably connected into bore 21B. In operation, the crossover block 21 can be lowered by tubing string 10. After block 21 is at its desired location in the well bore, tubing string 12 can be lowered and guided into alignment with bore 21A by guide funnel 23. Bore 21A has upwardly facing shoulder 25 upon which tubing 12 comes to rest. Means for guiding and sealingly connecting a tubing into a vertical passage is well known; therefore, details of this will not be discussed.

The lower end of sucker rod string 16 is provided with a hollow sucker rod section 24. This extends through sealing means 26 downwardly to connect with barrel 28 of pump 26 as shown more clearly in FIGURE 2. Hollow tubular sucker rod section 24 extends through and has a sliding fit with annular plug 27 which is in bore 21B just below sealing means 26. Plug 27 is to give the pumped fluid, as indicated by the arrow, a smoother surface to follow and is preferably of the same material as is the string of tubing.

The lower end of section 24 is attached to a modified pump plunger 28. The lower end of plunger 28 is designated 28A and has conventional clearance with the interior of barrel 20. By conventional clearance, it is meant the amount of clearance ordinarily provided for pumping the oil from a particular reservoir in which the pump is to be used. The upper end portion of plunger 28 is designated 28B and has a reduced diameter from that of section 28A. For example, for a 2" pump, the diameter of section 28B may be .005 to .020 inch smaller than the bottom sections. Thus, plunger 28 can be called a stepped type plunger. The annular space between section 28B of the plunger and the interior of pump barrel 20 is designated upper clearance or film-shaping zone 30. This zone 30 has a thickness which corresponds with the desired thickness of the film of the viscoelastic material.

Attention will now be directed toward means of connecting the viscoelastic fluid within the tubing 10 to the film-shaping zone 30. This includes ring-like passage 32 in the wall of the plunger. Passage 32 has radial ports 34 opening upwardly and outwardly into film-shaping zone 30. Passage 32 is connected through conduit 36 to the hollow interior of lower polish rod section 24. The interior 38 of polish rod section 24 is connected by a lateral port 40 above seal 26 to the annulus 42 within tubing 10 exterior of pump rods 16. The upper end of annular space 42 is connected through line 44 through meter 46 to a pump and supply means 48. Line 44 is also provided with pressure gauge 50.

The lower end of pump barrel 20 is provided with a standing valve 52 and the lower end of plunger 28 is provided with a traveling valve 54. Standing valve 52 and traveling valve 54 operate in a conventional manner upon the reciprocation of plunger 28 by the sucker rods. The upper end of barrel 20 is connected through bores 21D and 21A to the producing string of tubing 12.

When it is desired to inject the viscoelastic liquid or other film forming material to aid in pumping a viscous oil, the apparatus of FIGURES 1 and 2 is installed in the well bore with the lower end within the oil level of the well. The plunger 28 is reciprocated in a conventional manner. The pumped oil flows through opening 39 in the upper end of the plunger through bores 21D and 21A to tubing string 12 as indicated by the arrows. During this reciprocation, viscoelastic material is being pumped downwardly through annulus 42, conduit 36 and out the ports 34 of annular ring 32 into film-shaping zone 30 to form a film on the wall of the interior of the plunger as the pump plunger is being reciprocated. The point of maximum turbulence of the pumped oil is at the upper end of the plunger. Continued pumping of the viscoelastic material at the point of maximum turbulence aids in maintaining a film on the wall of the interior of the barrel and the tubing 12.

The apparatus of FIGURE 1 can be modified in various ways. For example, it can be modified as shown in FIG- URE 3. FIGURE 3 is modified from FIGURE 1 primarily in that only one string of tubing is used and the string of sucker rods is hollow. In this system the viscoelastic fluid is injected downwardly from the surface through the passage 60 within the hollow sucker rods 16. The sucker rods passage 60 is connected to pump 48 at the surface. The lower end of tubing 10 is provided with a centered tubular guide member 62 which surrounds the sucker rod and has a longitudinal length about as long as the stroke of the pump. A seal 63 is provided between rods 16 and the lower end of guide member 62. In this modification, it is desired to coat the exterior of the sucker rod 16 as well as the interior of the tubing 10 which now becomes the production tubing. A port 64 is provided to establish fluid communication between the interior of sucker rod 16 and the clearance between the rod and cylindrical guide 62. This clearance can be about the same as the clearance of upper plunger section 28B. The lower end of the interior of the string of sucker rods is in fluid communication with conduit 36 as shown and described in connection with FIGURE 1. Ports 64 are sized and spaced in relation to the size of parts 34 so that a volume of fluid will pass outwardly through port 64 to coat the exterior of sucker rod 16 with a film similar to that coating the inside of the string of tubing itself. Another modification of FIGURE 1 is to have sucker rod string 16 hollow to the surface and eliminate tubing string 10. In such modification, the viscoelastic material is pumped down the interior of the hollow string of tubing and the produced viscous oil is pumped up through tubing string 12.

While only a limited number of embodiments have been shown, it is possible to produce various other modifications without departing from the spirit or scope of the invention.

I claim:

1. An apparatus for pumping fluid using a reciprocating plunger within a pump barrel and a pumped oil passageway extending from the pump barrel to the surface, the improvement which comprises:

said plunger having an upper section and a lower section, said upper section being of a smaller diameter than that of said lower section to form a film-shaping zone between the plunger and the interior of the pump barrel;

a first conduit means extending from the surface to the upper end of said pump barrel; and

second conduit means fluidly connecting said first conduit means and said film-shaping zone.

2. An apparatus as defined in claim 1 wherein said second conduit means includes ring-like passage within said upper section of said plunger, said ring-like passage having ports opening into said film-shaping zone.

3. An apparatus as defined in claim 2 including pump means for pumping a viscoelastic fluid down said first conduit means and wherein said passageway for produced oil is at producing string of tubing and including means connecting said producing string to the upper end of said pump barrel, and further wherein said upper section of said plunger has a diameter from about .005 to about .020 inch smaller than said lower section of said plunger.

4. An apparatus as defined in claim 3 wherein said first conduit means includes a supply string of tubing, said apparatus of claim 3 further including a string of sucker rods extending within said supply string of tubing, the lower end of said string of sucker rods having a hollow passage therein; annular means enclosing the annular space between said string of sucker rods and the lower end of such supply string of tubing, said string of sucker rods slidingly and sealingly extending through said annular means; the lower end of said string of sucker rods being connected to said plunger; conduit means connecting the hollow interior of said string of sucker rods with said ring-like passage; the hollow interior of said string of sucker rods being in fluid communication with the interior of said supply string of tubing.

5. A pump for use in a downhole location for pumping fluids therefrom which comprises:

a pump barrel having a standing valve at the lower end thereof;

a plunger mounted within said barrel and having a traveling valve located therein, the said plunger having an upper section having a diameter smaller than the diameter of said lower section of said plunger to form a film-shaping zone between said upper portion of said plunger and the interior of said pump barrel;

means for supplying fluid other than the pumped fluid to said film-shaping zone.

6. An apparatus as defined in claim 5 n which said last mentioned means includes a ring-shaped passage supported by said plunger, said ring-shaped passage having radial ports in fluid communication with said film-shaping zone and connecting means connecting said ring-shaped passage to a supply of film forming fluid.

7. An apparatus as defined in claim 6 in which said film forming fluid is a viscoelastic liquid.

8. An apparatus as defined in claim 6 in which said means for supplying fluid other than the pump fluid to said film-shaping zone includes a string of hollow sucker rods and including means connecting the upper interior of said string of hollow sucker rods to a source of said other fluid and means connecting the lower end of said hollow string of sucker rods to said ring-shaped passage.

9. An apparatus as defined in claim 8 including a string of tubing surrounding said string of hollow sucker rods, including means whereby oil pumped by said plunger flows upwardly within said string of tubing exterior of said string of hollow sucker rods; and including a tubular shaped guide means within said string of tubing and surrounding said string of hollow sucker rods, a port means within the wall of said string of hollow sucker rods, said port and said tubular guide member being of such length and design that said port is within said guide for the full stroke of said tubular sucker rod.

References Cited UNITED STATES PATENTS 1,768,633 7/1930 Reis. 1,817,659 8/1931 Weaver 103-204 1,930,839 10/1933 Kater et al. 2,567,513 9/1951 Haines 1031 ROBERT M. WALKER, Primary Examiner.

U.S. Cl. X.R. 

